1. Field of the Invention
This invention relates to a method for producing sheet tobacco to be used as a material of cigarettes or the like, and to an apparatus for executing the method. More particularly, it relates to a method for producing the sheet tobacco by bonding tobacco chips or small round pieces with an adhesive (those materials including tobacco powder which can constitute sheet tobacco will hereinafter be called "tobacco chips"), and an apparatus for executing the method.
2. Description of the Related Art
So-called cut tobacco is used as raw material of cigarettes or the like. In cutting process or other processes for making cigarettes, tobacco chips such as large and small chips, powder, or fibers of tobacco leaves are inevitably produced as the remnant. To recycle the tobacco chips, they are bonded together with an appropriate adhesive, mixed with a reinforcing material and a moisture retentive material, and rolled with rollers, thus obtaining sheet tobacco. The sheet tobacco is cut into small pieces, and then blended into new cut tobacco.
FIG. 2 shows a conventional sheet tobacco-manufacturing apparatus. In the apparatus, tobacco chips (i.e., raw material) are mixed, at a time, in a batch-type mixer 12, with an appropriate adhesive, and reinforcing and moisture-retentive materials, thereby producing wet small round pieces. These pieces are uniformly distributed to constant feeders 14 provided for, for example, ten processing lines (only two of them are shown in FIG. 2), respectively.
The wet small round pieces are kneaded by a kneader 16 provided in each processing line, and then supplied to a shaping machine 18, thereby producing a wet sheet of tobacco. Subsequently, the wet sheet is dried by radiant heat of a heater or hot air while they are transferred by a mesh conveyor 22, and then cut by a cutter 24 into pieces of a substantially predetermined size. The pieces are gathered from the lines, and packed by a packing machine 26.
FIGS. 3 and 4 show examples of the kneader 16 and shaping machine 18, respectively. The kneader 16 has two pairs of rollers 34-37 to be driven by a motor 32, one pair being aligned with the other pair in the vertical direction. The distances between the rollers 34 and 35 and between the rollers 36 and 37 are approx. 0.2 mm. The shaping machine 18 has a pair of rollers 44 and 45 to be driven by a motor 42. The distance between the rollers 44 and 45 is approx. 0 mm.
As is indicated by the arrows shown in FIG. 3, the wet small round pieces supplied from the mixer 12 are successively fed from the upper end of the kneader 16 to the first rollers 34 and 35. As is shown in FIG. 5, a predetermined amount of wet small pieces 10a is deposited on the rollers 34 and 35 at all times, and the pieces deposited is kneaded between the rollers in accordance with rotation thereof made in the directions indicated by the arrows, and discharged from between the rollers, thus obtaining a sheet intermediate 10b.
In the above process, the rollers 34 and 35 rotate at different speeds, and the sheet product 10b is discharged, while being attached to the surface of the roller 35 rotating at a higher speed than the other roller 34. A doctor blade 38 is provided on the roller 35 tears the sheet product 10b from the roller 35.
The sheet intermediate 10b torn from the surface of the roller 35 is fed to the second rollers 36 and 37 of the kneader 16, where it is kneaded as done between the first rollers 34 and 35. Then, the intermediate 10b is discharged therefrom.
Subsequently, the sheet intermediate is fed to the rollers 44 and 45 of the shaping machine 18, processed in a way similar to the above-described one, and discharged therefrom, as is indicated by the arrows shown in FIG. 4.
In the above-described apparatus, the speed at which the rollers 44 and 45 of the shaping machine 18 can take the sheet intermediate discharged from the kneader 16 into the gap herebetween is limited, which determines the manufacturing speed. Accordingly, to obtain high manufacturing efficiency, the apparatus must incorporate, for example, as many as ten process lines, as is described above.
To eliminate this disadvantage, a method has been proposed in which the wet pieces discharged from the mixer 12 are directly supplied to the shaping machine 18, without using the kneader 16. However, final sheet products obtained by this method tend to be cracked when they are torn from the rollers of the shaping machine 18 due to low intensity of them. The greater the rotational speed or feeding speed of the shaping rollers, the more liable the sheet product is to be cracked.